This invention relates to turbo compressors in general and, in particular, to a new and useful method and system of limiting the discharge pressure of compressors by means of a blowoff control, in which the pressure behind the compressor is measured and one or more blowoff valves, arranged behind the compressor, are actuated by a controller when the blowoff line in the pressure flow diagram or the set maximum pressure is reached.
A method of achieving discharge pressure limitations by means of blowoff control by limiting the actual flow rate is already known. This known method, however, is unsuitable in the presence of very steep blowoff lines because the desired value together with the control deviation changes only slightly through increased pressure. In addition, this method has the disadvantage that when limiting the actual value, the overall amplification of the control circuit is reduced, thereby causing the control to react more slowly. Shifting of the blowoff line with the temperature also shifts the desired value of the discharge pressure limitation. A pressure limitation by a horizontal blowoff line is not possible because no defined set point for flow rate is then associated with a particular discharge pressure so that control of the system becomes unstable.